Check both hot and cold----------------
Check both hot and cold water valves at the hot water tank to make sure they are open fully. The cold water valve could be only part of the way open. My shower head will do the same thing while taking a shower. I have to leave the "OXYGENICS" shower just slitely cracked to a dribble, or I will get a shot of hot water as I turn the water back on at the little turn off valve while showering. For some reason the hot water pressure mixing will over come the cold water pressure for just a short time.
You could have a bad faucet that is allowing hot water to leak back into the cold water line at the mixing valve of the faucet.
Does this happen in the kitchen, shower or lavatory in the bath? If it is the bath, replace the shower head with a "OXYGENICS" head and a shut off valve at the shower head. By leaving the valve just cracked open to a dribble while conserving water.
Sid, Lois & HRH MISSY Terrible 2s SHIH TZU
2011 ROCKWOOD 8285 WS
2014 F-250 KING RANCH PS/SD/6R140/BFT
BOLIY PRO 3600SI GEN
DAYS CAMPED 2016 57 DAYS